Why is too much glucose harmful?

Question

I learned the citric acid cycle in biotechnology school and how cells work; about ADP and ATP and how the Cellular respiration (C6H12O6 + 6O2 -> 6CO2+6H2O) works.I am interested in understanding why exactly too much glucose is harmful, e.g. when having diabetes.What happens inside the cells so that the organs get damaged over time? Why can't the cells not simply "ignore" the needless glucose or convert it into energy?

Answer 1

There are many mechanisms responsible for high glucose being toxic to cells and tissues. The higher blood glucose leads to high glucose level in the interstitial fluid and inside the cells - intracellular. The glucose acts as a substrate for non-enzymatic reaction called "glycation", which is basically glucose being covalently linked to macromolecules especially to the intracellular and extracellular proteins. The non-enzymatic glycation of the protein may impede its function. Ultimately resulting reduced cell function and tissue function such as kidney, eye and nerve damage. The other mechanism involve higher metabolism rate. High glucose leads higher than normal metabolism, which generates free radicals. The free radicals damage macromolecules in different manner than gluycation.